For \(\lambda <0\) , the deformation turns point particles into finite size hard rods with length \(-\lambda e_s(u_j)\) . Therefore, the effective length, which describes the `free space' between the rods, is reduced and becomes \(L+\lambda Q_N^{(s)}\) . For \(\lambda >0\) , the distances between the particles are increased and the effective length become larger. This interpretation was first proposed in non-relativistic models [1]}, [2]}, [3]}. Here we see a natural generalization to the relativistic case.
